1. Field of the Invention
The present invention relates to a brake device for a vehicle and more particularly, to an integrated brake device for a vehicle, which may reduce the overall size and weight of a brake device to reduce the manufacturing costs, and may improve the mountability within the vehicle to facilitate the layout design.
2. Discussion of Related Art
In recent years, the development of hybrid vehicles, fuel cell vehicles, electric vehicles, and the like has been actively conducted in order to improve fuel efficiency and reduce emissions.
In these vehicles, a brake system, that is, a brake device for a vehicle is essentially installed, where the brake device for the vehicle refers to a device that functions to stop a running vehicle or reduce the speed thereof.
As examples of a typical brake device for a vehicle, a vacuum brake which generates a braking force using suction pressure of a vehicle engine and a hydraulic brake which generates a braking force using hydraulic pressure may be given.
The vacuum brake is a device that enables a vacuum booster to exert a large braking force with a small force by using a pressure difference between the suction pressure of the vehicle engine and the atmospheric pressure. That is, the vacuum brake refers to a device that generates a much greater output than the force applied to a brake pedal when a driver steps on the brake pedal.
Such a conventional vacuum brake has a problem that the suction pressure of the vehicle engine should be supplied to the vacuum booster in order to form vacuum, and thereby the fuel efficiency is reduced. In addition, the conventional vacuum brake also has a problem that the engine should be continuously driven in order to form vacuum even when the vehicle is stopped.
In addition, in cases of the fuel cell vehicle and the electric vehicle, there is no engine, and thereby it is impossible to apply an existing vacuum brake for amplifying a pedal stepping force of the driver when the vehicle is braked, and in a case of the hybrid vehicle, an idle stop function should be implemented when the vehicle is stopped in order to improve the fuel efficiency, and thereby the introduction of a hydraulic brake is required.
That is, as described above, in all vehicles, regenerative braking implementation is required in order to improve the fuel efficiency, and therefore the function of a hydraulic brake may be easily implemented at the time of the introduction of the hydraulic brake.
Meanwhile, an electro-hydraulic brake system which is a kind of the hydraulic brake is a brake system in which an electronic control unit detects, when a driver steps on a pedal, this, and a brake hydraulic pressure is transmitted to wheel cylinders (not shown) of each wheel to thereby generate a braking force.
An example regarding such an electro-hydraulic brake system has been disclosed in detail in U.S. Patent Publication No. 2012-0167565, entitled “Brake system including electric servo brake”.
In the electro-hydraulic brake system disclosed in the above Patent Publication, a master cylinder having primary and secondary pistons provided therein is installed so that hydraulic pressure is supplied to two brake circuits connected to wheel sides of the vehicle in response to the operation of a brake pedal. In addition, a servo brake including a working piston which is operated by a motor is installed inside the master cylinder. The working piston is provided to be linearly movable through a rack gear driving device, and the rack gear driving device includes a worm wheel which meshes with a worm shaft of the motor, and a rack gear that is linearly movable in a state of meshing with the worm wheel. That is, in the rack gear driving device, two worn wheels are installed to mesh with facing both sides of the rack gear, so that a linear motion of the rack gear is guided through the other worm wheel while the linear motion of the rack gear is conducted through one worm wheel.
However, in the conventional electro-hydraulic brake system having the above-described configuration, two worm wheels to which a pinion gear and a worm gear are coupled are used while they mesh with the both sides of the rack gear in order to secure straight advance property of the rack gear which pushes a piston within a pump so as to generate a brake hydraulic pressure, and therefore the size of the rack gear driving device is increased and the weight thereof is excessively increased. This results in a reduction in the mountability within the vehicle and degradation in the layout design.
In addition, in the conventional electro-hydraulic brake system, an ECU (electronic control unit) for controlling the position of a motor and an ECU for controlling a solenoid valve are separately installed while an ABS (anti-lock brake system) module and an ESC (electronic stability control) module for implementing the functions of ABS and ESC are independently installed, and therefore the overall size and weight of the brake system are increased, thereby increasing the manufacturing costs and reducing the mountability within the vehicle.